Question

We have an existing Windows Phone 7 project using C# and XNA.

To our surprise, the project built and ran just fine on a Nokia 820 with Windows Phone 8. We merely had to open the project in Visual Studio 2012 for that to happen.

Is there any reason to switch to a new Windows Phone 8 project? Any performance reasons or APIs we won’t have access to?

Answer 1

a full blown WP8 only project does not support XNA. you might want in app purchase in your XNA app.. which can be done using reflection… WP8 only project requires you to go C++ / DX

From msdn
XNA Framework support. You can develop XNA Framework apps that run on Windows Phone 8. To do this, you must set the target to Windows Phone OS 7.1. For more info, see XNA Framework and Windows Phone 8 development.

main highlights in additions to xna assembly usage are as below
• XNA Game Studio 4.0 apps that target Windows Phone OS 7.1 remain fully supported and continue to run on Windows Phone 8 devices.

• You can continue to develop and maintain new or existing XNA Framework apps that target Windows Phone OS 7.1.

• You can’t upgrade existing XNA Framework apps that target Windows Phone OS 7.1 to target Windows Phone OS 8.0.

• You can’t create new XNA Framework apps that target Windows Phone OS 8.0. When you select an XNA Game Studio 4.0 project template, you can only choose Windows Phone OS 7.1 as the target operating system.

• You can use certain XNA Framework assemblies in apps that target Windows Phone OS 8.0.